Vapor generating and superheating unit



y 1958 R. H. EVANS ETAL 2,835,231

VAPOR GENERATING AND SUPERHEATING UNIT Filed May 19, 1953 I 4 Sheets-Sheet 1L Richard fliv/azzs friedr/c/y B814 (f/m er INVENTORS ATTORNEY May 20, 1958 R. H. EVANS ETAL VAPOR GENERATING AND SUPERHEATING UNIT 4 Sheets-Sheet 2 Filed May 19, 1953 FIGZ.

INVENTORS ATTORNEY May 20, 1958 R. H. EVANS ET AL 3 VAPOR GENERATING AND SUPERHEATING UNIT Filed May 19. 1953 4 Sheets-Sheet 3 z'c/mrd fli'vans friedric/z Bali/mar INVENTORS ATTORNEY May 20, 1958 Filed May 19, 1953 R. H. EVANS ET AL VAPOR GENERATING AND SUPERHEATING UNIT 4 Sheets-Sheet 4 fife/yard Evans Friedricfi Beuzfhner INVENTORS ATTORNEY United States Patent VAPOR GENERATING AND SUPERHEATIN G UNIT Richard H. Evans, Surbiton, and Friedrich Beuthner, Hendon, England, assignors to The Babcock & Wilcox Company, New York, N. Y., a corporation of New Jersey Application May 19, 1953, Serial No. 355,994

6 Claims. (Cl. 122-478) This invention relates to vapor generators and in particular to an improved superheater and reheater arrangement for such vapor generators.

As improved efiiciencies are sought by the adoption of higher temperatures and pressures, difficulties are experi enced, when firing with an ash bearing fuel, in imparting the requisite temperature of superheat to the generated vapor, which may be required, for example, at a pressure of 1600 pounds per square inch and a temperature of 1000 F., particularly if the vapor is to be reheated to a like temperature. On the one hand a high gas temperature drop in the vapor heating portion of a unit is desirable in order to effect the requisite heat exchange and on the other hand slagging of the vapor heating surfaces in the neighborhood of the gas inlet to the said portion must be avoided or limited to a degree which can be tolerated. An object of the invention is the provision of vapor gen erating and superheating units suitable for use at high vapor pressures with ash-containing fuels and having im proved superheater and reheater arrangements for effecting high temperatures of superheat and reheat.

A tubular vapor generating and vapor heating unit in accordance with the present invention comprises a radiant vapor generating section, a drainable radiant superheater located within a zone adjacent the gas outlet from the radiant vapor generating section, and including tube lengths lining wall surface of the zone and tube lengths disposed in tube panels relatively widely spaced apart within the zone and a convection superheater and a drain able convection reheater disposed in the gas flow path beyond the said zone.

The invention will now be described, by way of example, with reference to the accompanying partly diagrammatic drawings, in which:

Figure 1 is a side elevation of a tubular steam generating, steam superheating, and steam reheating unit, in sectional view on a plane indicated by the lines 1-1 in Figures 3 and Figure 2 is a sectional plan view on the line II--II of Figure 1; t

Figure 3 is a front elevation of a rear part of the unit in section on a plane indicated by the lines III-III in Figures 1 and 4;

Figure 4 is a side elevation of the rear part of the unit in section on the line IV--IV of Figure 3;

Figure 5 is a rear elevation of part of the unit in section on the line VV of Figure 1;

Figure 6 is a plan view to a larger scale of part of a wall in section on the line VIVI of Figure 1; and

Figure 7 illustrates bifurcations in certain steam generating wall cooling tubes.

Referring to the drawings, the unit comprises a furnace chamber 1 fired through its front wall 2 by two pulverized fuel burner groups 3 and 4 associated with two respective compartments 5 and 6 into which the furnace chamber is divided. The front wall 2, opposite side walls 7 and the rear wall 8 of the furnace chamber are lined. with Patented May 20, 1958 steam generating cooling tubes supplied with water by respectivc lower headers 9, 10, and 11.

The compartments 5 and 6 of the furnace chamber are provided with respective hopper bottoms 12 and 13, of which the throats extend parallel to the side walls 7. The

a division wall 14 between the two compartments also eX- tends parallel to the side walls 7 and is formed of steam generating tubes, alternate tubes of which receive their water from a header 15 at the bottom of the compartment 5 while the remaining tubes receive their water from a header 16 at the bottom of the other compartment 6.

The discharges from all the steam generating tubes of the unit enter a steam and water drum 20 disposed forwarclly of the front wall 2 with its axis parallel thereto. The downcomer tubes 21 connected at their upper ends with the drum 2t) by smaller tubes 22 making connection with the bottom of the drum at points distributed along the length thereof and at their lower ends connected by tubes (not shown) to the headers 9, 10, 11, 15, and 16.

The rear wall 3 in its upper part is bent upwardly and forwardly, and then upwardly and rearwardly at a steep inclination, to form an arch 23 above the level of the burner groups. Above the level of the arch is a radiant superheating zone 24 receiving the gases flowing vertically upwardly past the arch, which zone has a laterial gas outlet 25 at the rear thereof leading to a lateral gas pass 26 arranged to conduct the gases from the zone to the top of a gas downpass 27.

The division wall 14 between the two compartments is closed over most of its area but over a region 18 forwardly of and below the arch 23 alternate tubes are bent into one compartment and the remaining tubes into the other compartment, whereby the gases may flow from one compartment to the other in the case of a difference of pressure therebetween. The division wall extends vertically upwardly above the level of the arch, dividing the radiant superheating zone 24, and extends rearwardly thereof into the lateral gas pass 26 about one-third of the distance from the lateral gas outlet 25 to the front of the gas downpass 27. I

At a level about half-way between the arch 23 and the tops of the burner groups is a horizontal U-shaped header 19 having a center limb 28 extending across the front wall 2 and side limbs 29 extending in the side Walls 7 rearwardly to positions vertically below the front of the arch 23. The central limb forms outlets header means for a row of radiantly heated superheater tubes 36 spaced 10 /2 to the rear of the inner surface of the front wall 2, and extending downwardly from the roof 31 of the radiant superheating zone to a position about 3' 6" above the U-shaped header 19, where they are bent to enter the front wall normally before curving downwardly to enter the top of the center limb 28 of the header. The side header limbs 29 form inlet header means for similar rows of radiant superheating tubes 32 similarly lining the side walls 7 above the header limbs and extending through the roof 31. The radiant superheating tubes of the row 36 leave, above the roof 31, the top of the steam and water drum 2%. The tubes of the rows 32 above the roof 31 enter respective headers 33, parallel to the side walls,l

which are connected to pass their steam to a header 34 extending parallel to the front wall above the roof 31.

As shown by Figure 7, the wall surface lined by the superheater tube row 30 is provided with steam generating tubes 35 which alternate with the superheating tubes and receive their fluid from the steam generating tubes therebelow through bifurcations or junctions 36 for halving the number of steam generating tubes. Figure 6 shows how the tubes 30 pass between the tubes 35 adja-.

cent to the bifurcations. Similar bifurcations and tube r 3 arrangements are used at the side walls 7 in association with the s'uperheat'er tube rows 32.

The steam generating tubes of the front wall connect at their upper ends directly into the steam and water drum 20. Those steam generating tubes (not shown) of the side walls 7 below the arch 23 are appropriately bent rearwardly along the side walls of the lateral gas passage 26. All the discharges from the side wall steam generating tubes flow to the steam and water drum 2% via headers 40 arranged parallel to and above each side wall. Most of the steam generating tubes of the rear wall 8 line the floor 41 of the lateral gas pass 26, then extend upwardly as a screen 42 between the lateral gas pass and the top of the gas downpass 27, and then line the roof 43 of the lateral. gas pass and the roof 31 of the radiant superheating zone, after which they enter the steam and water drum. Some of the steam generating tubes of the rear wall, however, extend as a screen 4-4 formed of a single row of tubes across the lateral gas outlot 25, after which they also line the roof 31 of the radiant superheating zone.

Radiant superheating tubes are arranged in the radiant superheating zone in the form of three rows each extending parallel to the front wall 2 of tube platens or panels each parallel to the side walls 7. The front row comprises eight platens 45, each consisting of ten tubes extending side by side, receiving their steam from the transverse header 34, extending vertically downwardly through the roof 31 and to the bottom of the radiant superheating zone, where they are bent and pass downwardly and rearwardly to the arch 23 which they pierce and enter a respective superheater box 46. Four platens of the rov. are disposed to each side of the division wall 14, with a distance of 4' betwen adjacent platens, a distance of 4 between the inner platen and the division wall 14, and a distance of 4 between the outer platen and the side wall 7.

Eight steam generating tubes 17 of the rear wall 3 of the furnace chamber leave the rear wall at the arch 32 and extend forwardly and upwardly as screens below and in front of the respective inclined lower parts of the platens 45 of the front row of platens, subsequently passing upwardly to the drum 20 in company with the tubes of the front wall 2.

The platens of the second and third rows 47 and 48 respectively similarly consist of ten tubes, and are similarly spaced from one another and from the division wall 14 and from the side walls 7. The tubes of each second row platen are continuous with respective tubes of a respective third row platen and are shaped in the manner of a hairpin with their return bends 49 uppermost and above the roof 31. The major and upper parts of the second and third rows of platens are vertical but the lower parts of the tubes are inclined downwardly and rearwardly. The tubes of the second row of platens are connected to respective superheater boxes 46; the tubes of the third row of platens, after passing through the arch 23, and being led a certain distance rearwardly therefrom, are led downwardly in front of the gas downpass 27 to enter a horizontal U-shaped header 37 having its center and side limbs 59 and 51 respectively at the bottoms of the front 52 and opposite side walls 53 of the gas downpass-27. Steam tubes 57 from the header limbs 51 line the side walls 53 of the gas downpass and enter the side limbs 54 of a horizontal upper U-shaped header 33 above the roof of the gas downpass, the center limb 55 of which upper U-shaped header is above the gas downpass rear wall 56. The center limb S of the lower U-shaped header passes steam upwardly in steam tubes 39 lining the gas downpass front wall 52, which tubes after passing behind the screen 42 across the gas flow path from the lateral gas pass 26 to the top of the gas downpass 27, line the roof 6%) of the gas downpass 27 and enter the center limb 55 of the upper U-shaped header.

The center limb 50 of the lower U-shaped header also passes steam to a row 61 of tubes leading horizontally across the bottom of the gas downpass 27 to the rear wall 56 thereof, which they line, entering at their upper ends into the center limb 55 of the upper U-shaped header.

Near the top of the gas downpass 27 is a primary section 62 of convection superheater, the tubes of which are horizontally extending and are drainable, and which is supplied with steam through an inlet header 63 from the center limb 55 of the upper U-shaped header. The steam passes through the primary convection superheater section 62 in counterflow to the gases flowing thereover, leaves via an outlet header 64, and is arrange to pass via an attemperator 65 to a secondary section 66' of convection superheater arranged in the lateral gas pass 26'. The inlet header 67 and the outlet header 6?; are arranged above the roof of the lateral. gas pass, and extend parallel to the steam and water drum Ztl. The inlet header 67 lies forwardly of the outlet header as, and the superheater tubes from the former header extend vertically downwardly in four rows through the lateral gas pass roof 43 to adjacent the floor 4-1 of the lateral gas pass, whereupon they are bent rearwardly and extend vertically upwardly again to near the roof; in this part of the secondary convection superheater section the tubes are arranged in planes parallel to the side walls and l apart. The superheatcr tubes are then brought into two rows only, the distance between adjacent tubes in the same row being 6", which rows extend rearwardly and then vertically downwardly and then upwardly and through the lateral gas pass roof 43 to the outlet header 68, from which the steam is taken to the point of use, e. g. a turbine.

A primary section 69 of convection steam reheater, divided into three banks arranged in series as regards steam flow therethrough and gas flow thereover, is disposed in the gas fiow pass below the primary convection superheater section 62. Each primary reheater bank con sists of horizontally extending tubes. Through the primary reheater section 69 steam to be reheated, e. g. steam from an intermediate stage of the turbine, is arranged to flow from a lower inlet header 70 in counterflow to the gas flow to an upper outlet header 71. The reheated steam is led therefrom via a reheater attemperator 72 to a secondary section 73 of convection reheater disposed in the gas flow path between the secondary section 66 of convection superheater in the lateral gas pass 24 and the primary section 62 of convection superheater in the gas downpass 27.

The secondary reheater section 73 comprises six rows 74 of tubes extending horizontally across the gas downpass 27 above the primary convection superheater section 62, and passing through the uppermost part 75 of the front wall 52 of the gas downpass 27 into the lateral gas pass 26, in the rear part of which they are bent upwardly and extend as hairpin-like parts with return bends 76 uppermost and above the lateral gas pass roof 43. Both the secondary reheater section outlet header 78, from which latter the reheated steam is led to a point of use, e. g. a later stage of the turbine, are behind the gas downpass rear wall 56.

In the region of the primary section 69 of convection steam reheater the gas downpass 27 is divided by vertical partitions 80 into three parallel passages. The primary reheater section 69 occupies only the center passage 81, each of the two side passages 82 containing two banks of economizer tubes 83. Dampers 84 are provided in the side passages 82 below the economizer banks 83, by which the distribution of the gases between the passages can be controlled.

Below the three gas passages 81 and 82 the downwardly flowing gases reunite before flowing to the main economizer banks 83, which are arranged in two groups, one group to each side of a central passage 86 providing a gas by-pass through which gases may flow, under control of dampers 87, to by-pass the main economizer banks.

The reference numerals 90 indicate the lower parts of various top-supporting means for items of the unit.

The reference numerals 95 indicate the positions of soot blowers of the kind having a blowing angle of 360, and the reference numerals 96 indicate the positions of soot blower having a more restricted blowing angle.

In service, the drainability of the superheater wall tubes 30 and 32 and the superheater tube panels 45, 47, and 48 and of the reheater sections 73 and 81 enables the safety thereof during starting to be ensured.

During operation, the combination of radiant and convection superheater provides a relatively flat superheat temperatureload curve and the use of superheater tube panels 45, 47, and 48 and superheater wall tubes 30 and 32 enables high temperatures of superheat and reheat to be attained. The tube panels help to limit radiation to the wall tubes and to one another by limiting the distance through which radiation may occur. If slagging occurs on the tube panels the danger of bridging is avoided owing to their Wide spacing, whilst provision is made for the introduction of cleaning fluid to blow over the panels. Further, provision is made for the introduction of cleaning fluid rearwardly of the tube panels between the panels and the section 66 of superheater in the lateral gas pass 26. Simple and direct connections for the vapor are provided between the vapor and liquid drum 20, the superheating Wall tubes 30 and 32, and the tube panels, and the tube panels are simply but efiectively supported by means outside the gas flow pass. The provision in association with the reheater of the attemperator 72 as well as gas by-pass passages 82 enables substantially instantaneous and accurate regulation of reheat to be achieved.

We claim:

1. A vapor generating and superheating unit com prising front, rear, and side walls defining a vertically elongated chamber having a laterally disposed gas outlet in the upper portion thereof, a liquid and vapor drum structurally supported above said chamber, a multiplicity of vapor generating tubes arranged along said chamber Walls and connecting into said liquid and vapor drum, means for burning fuel in the lower portion of said chamber and producing a heating gas flow upwardly therein and thence laterally through said gas outlet, a plurality of radiant superheater tubes extending from the liquid and vapor drum to a position intermediate the height of said chamber and lining the front wall of said chamber, a Wall header disposed in the front and side walls of said chamber connected to the lower end of said superheater tubes, an intermediate header disposed above said chamber, additional superheater tubes extending from said wall header along said side walls and connecting into said intermediate header, a collecting header disposed at the rear of said chamber, a row of widely spaced superheater tube platens arranged across said chamber and connected to said intermediate header and said collecting header, and a row of widely spaced inverted hairpin superheater tubes connected to said collecting header and extending across said chamber rearwardly of said superheater tube platens.

2. A vapor generating and superheating unit comprising front, rear and side walls defining a vertically elongated chamber having laterally disposed gas outlet in the upper portion thereof, a liquid and vapor drum structurally supported above said chamber, a multiplicity of vapor generating tubes arranged along said chamber walls and connecting into said liquid and vapor drum, means for burning fuel in the lower portion of said chan bet and producing a heating gas flow upwardly therein and thence laterally through said gas outlet, a plurality of radiant superheater tubes extending from the liquid and vapor drum to a position intermediate the height of said chamber and lining the front wall surface of said chamber, a wall header disposed in the front and side walls of said chamber connected to the lower end of above said chamber, a secondary group of radiant superheater tubes extending from said wall header along said side walls and connected into said intermediate header, a collecting header disposed at the rear of said chamber below said convection heating pass, a row of superheater tubes platens having their upper ends connected to said intermediate header and extending vertically downward into said chamber to a position below said gas outlet and then at an inclination through said rear wall to said collecting header, and a row of groups of inverted U- shaped superheater tubes connected to said collecting header and extending across said chamber rearwardly of said superheater tube platens.

3. A vapor generating and superheating unit comprising front, rear, and side walls defining a vertically elongated chamber having a laterally disposed gas outlet in the upper portion thereof, a liquid and vapor drum structurally supported above said chamber, a multiplicity of vapor generating tubes arranged along said chamber walls and connecting into said liquid and vapor drum, means for burning fuel in the lower portion of said chamber and producing a heating gas flow upwardly therein and thence laterally through said gas outlet, a group of radiant superheater tubes extending from the liquid and vapor drum to a position intermediate the height of said chamber and lining the front wall of said chamber, a wall header disposed in the front and side walls of said chamber, connected to the lower end of said superheater tubes, an intermediate header disposed above said chamber, a second group of radiant superheater tubes extending from said wall header along said side walls and connected into said intermediate header, some of said vapor generating tubes having lower bifurcated portions below said superheater tubes and upper portions alternating with said superheater tubes along the upper portion of said chamber, a collecting header disposed at the rear of said chamber below said convection heating pass, a row of widely spaced superheater tube platens having their upper ends connected to said intermediate header and extending vertically downward into said chamber to a position below said gas outlet and then at an inclination through said rear wall to said collecting header, and a row of Widely spaced groups of inverted U-shaped superheater tubes connected to said collecting header and extending across said chamber rearwardly of said superheater tube platens.

4. A vapor generating and superheating unit comprising walls defining a vertically elongated chamber having a heating gas outlet in the upper portion of said chamber, a laterally extending gas pass opening at one end to said gas outlet, an upright convection gas passage arranged laterally adjacent and opening to the opposite end of said gas pass, means for burning fuel in the lower portion of said chamber and producing a heating gas flow upwardly therein, a liquid and vapor drum structurally supported above said chamber, a radiant superheater located in the upper portion of said chamberadjacent said gas outlet, said radiant superheater comprising closely spaced tubes extending along a portion of said walls and having their inlet ends connected to said liquid and vapor drum, and a plurality of widely spaced tube platens distributed across said chamber, each of said tube platens comprising a plurality of upwardly extending horizontally spaced vapor heating tubes, means for connecting the outlet ends of said wall tubes to said tube platens for supplying vapor thereto, a primary superheater disposed in said convection gas passage and connected for series vapor flow from said tube platens, and a secondary superheater positioned in the gas entrance end of said laterally extending gas pass and connected for series vapor flow from said primary superheater.

5. A vapor generating and superheating unit comprising front, rear and side walls defining a vertically elon-v gated chamber having a heating gas outlet in the upper eese-a1 portion of said chamber, a laterally extending gas pass opening at one end to said gas outlet, an upright convection gas passage arranged laterally adjacent and opening to the opposite end of said gas pass, means for burning fuel in the lower portion of said chamber and producing a heating gas flow upwardly therein, a liquid and vapor drum structurally supported above said chamber, a radiant superheater located in the upper portion of said chamber adjacent said gas outlet, said radiant superheater comprising closely spaced tubes extending along a portion of said front. Wall and having their inlet ends connected to said liquid and vapor drum, and a plurality of widely spaced tube platens distributed across said chamber, each of said tube platens comprising a plurality of upwardly extending horizontally spaced vapor heating tubes, means for connecting the outlet ends of said front wall tubes to said tube platens for supplying vapor thereto, a primary superheater disposed in said convection gas passage and connected for series vapor flow from said tube platens, and a secondary superheater positioned in the gas entrance end of said laterally extending gas pass and connected for series vapor flow from said primary superheater.

6. A vapor generating and superheating unit comprising front, rear and side walls defining a vertically eiongated chamber having a heating gas outlet in the upper portion of said chamber, a laterally extending gas pass opening at one end to said gas outlet, an upright convection'gas passage arranged laterally adjacent and opening to the opposite end of said gas pass, means for burning fuel in the lower portion of said chamber and producing a heating gas flow upwardly therein, a liquid and vapor drum structurally supported above said chamber, a radiant superheater located in the upper portion of said chamber adjacent said gas outlet, said radiant superheater comprising closely spaced tubes extending along a portion of said front and side walls, and a plurality of widely spaced tube platens distributed across said chamber, said front wall tubes having their inlet ends connected to said liquid and vapor drum, means for supplying vapor from the outlet ends of said front wall tubes to the inlet ends of said side wall tubes, means for supplying vapor from the outlet ends of said side wall tubes to said tube platens, a primary superheater disposed in said convection gas passage and connected for series vapor flow from said tube platens, and a secondary superheater positioned in the gas entrance end of said laterally extending gas pass and connected for series vapor flow from said primary superheater.

References Cited in the file of this patent UNITED STATES PATENTS 2,213,185 Armacost Sept. 3, 1940 2,220,886 Cassidy Nov. 12, 1940 2,308,762 Krug et al. Jan. 19, 1943 2,424,476 Marshall July 22, 1947 2,730,080 Stallkamp Jan. 10, 1956 FOREIGN PATENTS 829,740 Germany Jan. 28, 1952 OTHER REFERENCES B & W Bulletin G 67A of 1950, page 41. 

